THREE MONTHS have passed since the killing of 20 schoolchildren and six adults in Newtown, Conn., and already the sense of urgency for new gun-control legislation is starting to wane. A poll by CBS News published March 26 shows that 47 percent of those questioned favor making gun laws more strict, down from 57 percent in December. Thirty-nine percent would keep laws as they are, compared to 30 percent after the shootings.

This is all the more reason why all eyes will be on the Senate after it returns from an Easter recess. The Judiciary Committee has sent four proposals to the floor for the first big test of whether the Newtown slayings will lead Congress to enact serious additional restraints on gun violence.

We were among those who hoped that the Newtown shootings — in which Adam Lanza mowed down the first-graders and staff at Sandy Hook Elementary School with a semiautomatic assault rifle, a Bushmaster XM15-E2S — would prompt Congress to reimpose the ban on such weapons. They were designed for war and have no place in hunting, target practice or self-defense. The previous, decade-long ban expired in 2004, and Sen. Dianne Feinstein (D-Calif.) has led the push for a replacement.

But politics must be the art of the possible. Unfortunately, support for Feinstein’s bill is insufficient in the Senate to defeat a filibuster. Majority Leader Harry M. Reid (D-Nev.) has announced that her proposal will be excluded from the baseline legislation but will get a separate vote as an amendment. Reid’s logic is sound; at this juncture, tactics matter. It is important that the Senate pass legislation, rather than just make a point.

At the same time, it is even more important that the Senate move to restrict high-capacity ammunition magazines. What makes a semiautomatic weapon dangerous is the ability to fire repeatedly without reloading. The danger is amplified by magazines that hold up to 30 bullets. If they are limited, say, to 10 bullets, forcing a shooter to change magazines could provide precious moments to save lives and stop the assailant. Mr. Lanza used 30-round magazines and got off at least 154 shots in five minutes. Unfortunately, Mr. Reid has not put a limit on high-capacity magazines in the baseline bill. We hope the Senate will have the wisdom to approve one as an amendment.

The Senate also is expected to vote on making background checks universal for gun purchases, which would close a major loophole that has allowed private sales to be conducted in the shadows. Still at issue are the record-keeping requirements. Currently, background checks at a gun dealer lead to a paper record that the dealer preserves for 20 years. While this system is cumbersome, it is better than nothing, and it provides law enforcement investigators with a starting point for tracing a gun used in a crime. We believe private sales should include similar record-keeping requirements, consummated at a licensed dealer, with a paper record. The gun debate has been predictably intense, but now comes the moment of truth. We hope the Senate will not falter.